1. Field of the Invention
The invention relates to a pedestrian guard for a motor vehicle for protecting persons in the event of collision with the motor vehicle.
2. Description of Related Art
In the event of a collision between a person, in particular a pedestrian, and a motor vehicle, the accident process is normally divided into three impact zones, namely the leg region, the hip region and the head region of the person impacted.
The leg impact takes place essentially in the region of the bumper of the motor vehicle, the hip impact takes place, in particular, in the region of the so-called lock connections, e.g., the connection of the lock of the front hood or bonnet to the frame of the motor vehicle, and the head impact has its essential danger points in the windscreen wipers, in the region of the hood in which the engine block lies directly underneath, and in the connection of the fenders to the upper auxiliary side member, i.e., the side member immediately underneath the joint between the fender and the hood.
This invention relates to a pedestrian guard which is intended to protect the person who suffers a hip impact and a head impact.
What is particularly problematic in the event of such an impact is the connection of the fender to the auxiliary side member, because the latter is being constructed with increasing stiffness in motor vehicles to provide homogeneous stiffness of the front section of the motor vehicle.
Since the front body sections, for example, the fenders and the front hood, not only act in an energy-absorbing manner, but they should also be stiffly constructed for normal use in other directions of loading, further demands are imposed here. In this case, particular consideration must be given to suction forces during travel and lateral forces on the fender, which forces may be generated when persons lean against the vehicle.
Apart from these planar connections, e.g., the connection of the fenders to the frame of the motor vehicle, punctual connection points, e.g., the bonnet lock connection, are also problem zones. The problem here lies not only in the installation conditions, but also in the fact that suction forces are generated in the direction opposite to the direction of deformation, so that different levels of force are required in a suitable collision guard under a tensile or compressive stress.
In this connection, a method is known in the prior art for providing deformable sheet steel straps at the connection of the fenders to the frame of the motor vehicle. The disadvantage of this design, however, lies in associated low torsional stiffness which has a negative effect in the case of forces which act laterally and are produced, for example, when a person leans against the vehicle.
A further disadvantage of the prior art design is the low energy absorption. As rectangular a force-distance curve as possible in the direction of protection is important in the case of a head impact.
A further problem arises from the fact that the mass of the head of children and adults differs considerably, the head of an adult being assumed at present to have a mass of 4.5 kg and the head of a child to have a mass of between 2.5 kg and 3.5 kg. Since the seriousness of injuries is measured in HIC's, and since the HIC value is a function of retardation, a higher retardation is automatically obtained at a lower mass, i.e., in the case of impact of the head of a child, if a deformation element is present, e.g., a deformable sheet steel strap with only one force stage.